No sooner had Democrats condemned Attorney General Jeff Sessions for meeting with the Russian ambassador than he began turning up in the darnedest places, namely alongside Democrats.

House Minority Leader Nancy Pelosi insisted Sunday her situation was “completely different” after she was called on a 2010 photo showing her at a dinner with Russian Ambassador Sergey Kislyak, despite her earlier insistence that she had never met with him.

“We were meeting with the president of Russia. He brought an entourage in with him. He was the one who was doing the talking,” Mrs. Pelosi said on CNN’s “State of the Union.”

“The question was, ‘Have you met with him?’ No, I haven’t met with him, I met with the president of Russia. Who else is in his entourage, who knows? Presidents, heads of states come in, they bring their party, they barely even introduce them,” Mrs. Pelosi said. “This is completely, completely different.”

The top House Democrat called last week for Mr. Sessions to resign for saying at his Jan. 10 confirmation hearing that he “did not have communications” with Russian officials during the campaign, even though it was later reported that he met twice in 2016 with Mr. Kislyak.

President Trump has responded by needling Democrats about their meetings with Russian officials, first by posting a 2003 photo Friday of Senate Minority Leader Chuck Schumer eating doughnuts at Krispy Kreme with Russian president Vladimir Putin.

“A total hypocrite!” Mr. Trump said in a tweet.

The president also tweeted out the photo of Mrs. Pelosi and Mr. Kislyak at the dinner with the message, “I hereby demand a second investigation, after Schumer, of Pelosi for her close ties to Russia, and lying about it.”

He was apparently referring to her Friday interview with Politico Playbook during which she was asked whether she had ever met with the Russian ambassador. Ms. Pelosi said, “Not with this Russian ambassador, no.”

Also coming under fire was Sen. Clarie McCaskill, Missouri Democrat, who said last week she had never met with the Russian ambassador.

“I’ve been on the Senate Armed Services Committee for 10 years, and in that time, have had no call from, or meeting with, the Russian ambassador. Ever. That’s because ambassadors call members of Foreign Relations Committee,” Ms. McCaskill said in a Thursday statement. “Attorney General Sessions should resign.”

Within hours, however, sharp-eyed Twitter users had produced tweets from her about a 2013 meeting with the Russian ambassador and a 2015 phone call.

“Looks like McCaskill is having trouble with the truth today,” Katie Martin, National Republican Senatorial Committee spokeswoman, told ABC News.

Sen. Marco Rubio, Florida Republican, said it would be nearly impossible for lawmakers to avoid ambassadors, whose job it is to connect with elected representatives and other influential Washingtonians.

“That’s what ambassadors do. I meet with dozens of ambassadors a year and I run into them all the time. That’s what they do,” Mr. Rubio told CNN’s “State of the Union.” “They are out there trying to reach people and talk to them, and so it’s not unusual for a member of the Senate can meet with an ambassador.”

Mr. Sessions insisted Thursday that he never met with Russian officials to discuss the campaign, calling such allegations “totally false,” but acknowledged that he “should have slowed down and said, ‘But I did meet one Russian official a couple of times,’ and that would be the ambassador.”

He also said he would send a letter clarifying his testimony to the Senate Judiciary Committee, as well as recuse himself from a federal investigation into Moscow meddling with the 2016 election.

The number of Democrats caught falsely saying they had never met with the ambassador, only to be reminded that they had and then providing “yes, but” rebuttals, suggested that such memory lapses in the life of a lawmaker are normal.

Mr. Rubio agreed it was “problematic” in terms of how Mr. Sessions answered the question during the confirmation hearing, but added that, “We’ve gotten to the point of hysteria here.”

As for accusations that Mr. Kislyak recruits spies, Mr. Rubio said it’s “not a mystery to anyone that — and I’m not talking about him in particular, just in general — that virtually every embassy in Washington, D.C., has some intelligence component associated with it.”

“That’s just the nature of diplomatic facilities, not just in Washington, but all over the world,” Mr. Rubio said. “But, in the end, again, I go to reiterate the point I’ve made earlier, and it is this. Ambassadors try to meet with senators and congressmen and people on the Hill all the time. It is what they spend a significant amount of their time doing. That is their job.”